1. Field of the Invention
This invention relates generally to a device for automatically detecting the end of a web, or of a break in the web, and for splicing therewith a new web. More particularly, the invention is intended for use in corrugated cardboard installations having a feed roller for feeding a web roll and preparing a new web roll for feeding through the installation when the first has been exhausted or breaks.
2. Description of the Prior Art
Corrugated cardboard installations with which the invention is intended for use generally include a control device which is movable, in dependence upon the feed web roll, into a state of readiness for automatic activation of a web-splicing operation. Such devices include web-sensing means which activate a control device to initiate splicing when the end of the web is reached or in the event a break in the web occurs. The control device controls operation of web-splicing means which include a web brake having a web storage space from which a fresh web supply is withdrawn during the web-splicing operation.
In order to achieve continuous feed of strip material to a processing machine, it is necessary to attach to the web which is being run to the machine on a first web roll a second web on a new supply roll at precisely the right time before the first web roll is exhausted. In order to keep waste of web material at a minimum, the first web roll should be unrolled as far as possible before the second web is attached.
A problem common to running a web of material through a processing machine is that the unused turns of web material at the end of the web roll may become damaged on the outer edges thereof, such that the web will tear before the roll is completely empty. After such a break in the web, the web must be re-fed into the processing machine resulting in down time of the machine. Furthermore, there is always a considerable amount of waste when a break occurs. It therefore is desirable to effect a web splicing operation at a time when there is as little as possible unused material on the web roll, and yet not too late such that a web break or tear may occur. A consideration in this regard is that when paper webs of relatively low quality are used in corrugated cardboard installations, the likelihood of a break near the end of the roll is high; even the slightest damage to such webs may result in breaking of the web.
It is known to employ devices for automatically splicing web material in web feeding installations. One such device is disclosed in U.S. Pat. No. 3,891,158 in which a control device is activated when the web roll reaches a given coil diameter. At the same time, the speed of the web running off the roll is slowed by a brake. At a subsequent work station, operations on the web supply continue. Sensors monitor the web which is travelling off the roll at decreased speed and detect any break or the end of the web. After the detection of such a break or the end, the feeding web is fully braked and stopped and the beginning of the new web is brought to the running-out end and attached to it. Thereupon the brake is released and the new web attached to the old web end is drawn off with increasing speed. The disadvantage with the patented device is that it requires extensive control equipment, as well as a large amount of web storage area. Additionally, such known devices are not capable of detecting web tears which may start at the edge of the web. If a web tear, as opposed to a break, is not immediately detected, activation of the web splicing process will take place too late. In such instances, automatic splicing operations are not practicable.